No surprises in most recent sea lamprey study

September 25, 2012

A surveying crew checking into sea lamprey populations in a few Presque Isle County streams found no surprises in a recent survey, and efforts to keep the parasite from breeding in the upper reaches of one river continue to show positive results.

Aaron Jubar, U.S. Fish and Wildlife Service fish biologist, said surveys conducted between Sept. 11-20 in Northeast Michigan showed populations of sea lamprey larvae to be mostly under control.

"We did not find anything that would need a treatment sooner than what we might be expecting," he said.

While in Presque Isle County, crews checked the lamprey populations in Ocqueoc River, Ocqueoc Lake and Schmidt Creek, Jubar said. Schmidt Creek is north of Rogers City, while the Ocqueoc empties into Hammond Bay, north of Onaway. Crews also surveyed Long Lake Creek, which drains its namesake lake into Lake Huron, north of Alpena.

To determine this, crews used a combination of techniques involving electrofishing and using a slow-release chemical known as bayluscide, Jubar said. The chemical, which affects lampreys almost exclusively, dissolves and breaks down rapidly, but not before aggravating lamprey larvae.

"The main difference between the two is when we're in a stream or river, we can go along and wade in there, and use the backpack electrofishers," he said.

The granular bayluscide is useful for deeper areas, especially if lampreys become established in an inland lake, Jubar said. As the pesticide slowly dissolves, it drives immature lampreys out of their burrows, eventually killing them. This gives surveyors a chance to check on a stream's population.

"We're always on the lookout for any new infestations, but also trying to keep up on the population and get an estimate of (it) on each stream on a regular basis," he said. "This gives us an ability to assign streams for treatment."

The Fish and Wildlife doesn't have the resources or manpower to treat every stream every year, Jubar said. Instead, they are treated on a cycle based in part on the survey results.

"Sometimes we're surprised with the number we may find in a stream, others we're pleasantly surprised because we don't find them where we had in the past," he said. "This means the stream's effectively treated or it's just not seeing the spawners return."

Scheduled treatments, combined with an electric lamprey barrier, have kept sea lampreys out of the upper reaches of the Ocqueoc River, Jubar said. The Ocqueoc connects many inland lakes and has a large number of tributaries, making it a very hard system to clear if it became entirely infested. Where the larvae were once found a considerable ways up the river, they're now largely contained between the lamprey weir and the river mouth.

Low stream levels due to this year's lack of rain and smaller spring flooding could also have limited the movement of spawning lampreys, Jubar said. The spring flooding in 2011 swelled rivers in their banks and made certain barriers ineffective.

"It's a little bit different (this year) because we've had such a drought and it's gone on for so long," he said.

Sea lampreys lack the instinct to return to the stream where they were spawned, Jubar said. How they pick a location is still being researched, but so far scientists have found they're drawn by phermones from females, who themselves are likely attracted by a stream's flowing water. This means crews can clear a stream of lampreys, only to find it's become infested again, sometimes several years later.

Once lampreys spawn, their larvae will burrow into soft, sandy river bottoms and live in burrows for a number of years, Jubar said. How fast they grow depends on water temperatures and the amount of food available to the juveniles, which filter-feed at this life stage. In Northeast Michigan, it typically takes three to five years before a larval lamprey can grow into a parasitic adult and enter Lake Huron.

At this stage, they latch on to predator fish like salmon, walleye and trout, and each one can destroy up to 40 pounds of fish before it returns to spawn after a year to 20 months, according to the Great Lakes Information Network.